Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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LOW-TO-MID-RANGE WATER REDUCTION
USING POLYCARBOXYLATE COMB POLYMERS
Field of the Invention
The present invention relates to modification of hydratable cementitious
compositions; and, more particularly, to plasticizing concretes and mortars
having a
relatively high water/cement ratio using a polycarboxylate comb type copolymer
having
5-23 linear repeating ethylene oxide units and being devoid of propylene oxide
or
higher oxyalkylene groups.
Backaround of the Invention
Water-reducing admixtures reduce the amount of water used for fluidifying
concrete mixes, and this means that the concrete needs less water to reach a
required
slump as compared to untreated concrete. A lower water-cement ratio (w/c) can
lead to
higher strength concrete without increasing the cement amount.
Polycarboxylate ("PC") type cement dispersants are known for high range water
reduction ("HRWR") whereby water content is reduced by 12-30 percent compared
to
untreated concrete. HRWR plasticizers are referred to as "superplasticizers"
and allow
concrete to be highly fluid and to be placed quickly with little or no
compaction efforts
required.
For example, US 6,187,841 of Tanaka et al. disclosed PC HRWR copolymers
having (alkoxy)polyalkylene glycol mono(meth)acrylic ester type monomers and
(meth)acrylic acid type monomers. However, this reference emphasizes the need
to
use large molecular sizes to achieve ideal water reduction conditions. In
another
example, EP 0 850 894 B1 of Hirata et al. disclosed PC HRWR polymers having
polyalkylene glycol ether-based monomers and maleic acid based monomers for
achieving high water reducing capabilities, and similarly disclosed molecular
size
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ranges extending upwards to 100,000. Both examples reflect preferences for
using a
large number of alkylene oxide groups.
In contrast to the extensive polycarboxylate polymer size and weight ranges
taught in these exemplary art references, the commercial reality in the
concrete industry
is that non-PC cement dispersants, such as lignin type plasticizers, are
primarily used
for low-to-mid-range plasticization of concrete mixes instead of HRWR PC
polymers. It
appears that polycarboxylate type polymers tend to be reserved for high range
water
reduction applications, i.e., for achieving the 12 to 30 percent reduction in
hydration
water that ordinarily would be deployed in HRWR applications.
It is an objective of the present invention to provide an alternative to
lignin type
water reducers, by achieving low-range and mid-range water reduction in
concrete and
mortar while using a polycarboxylate type cement dispersant copolymer, and
while also
achieving greater performance, in terms of admixture dosage efficiency at
lower water
cuts (i.e., below 12 percent water cut) as compared to conventional (e.g.,
larger,
commercial-scale) polycarboxylate type polymers that are typically used for
high range
water reduction (HRWR) applications.
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Summary of the Invention
In providing a performance improvement over prior art polycarboxylate (PC)
type
"superplasticizers" or HRWR cement dispersant polymers, the present invention
describes a method for achieving low-to-mid-range reduction of hydration water
in
concrete or mortar mixes using specifically sized PC copolymer constituents.
The present invention also reflects an unexpected and surprising improvement,
in terms of admixture dosage efficiency at certain high water-cement (w/c)
ratios, when
PC copolymers taught by the present invention were compared to commercial
reference PC polymers used in conventional HRWR applications.
Thus, an exemplary method of the present for achieving low-to-mid-range-
plasticizing of a hydratable cementitious composition using a polycarboxylate
copolymer, comprises: combining with water and cement to form a hydratable
cennentitious mixture, wherein the amount of water and cement is within a
water/cement
ratio (w/c) of at least 0.4 and more preferably at least 0.45, and further
wherein the w/c
ratio does not exceed 0.80 and more preferably does not exceed 0.75, at least
one
polycarboxylate comb type copolymer having the following monomer constituents:
(A) polyoxyalkylene monomer represented by structural formula:
R1 ,R2
\ /
C =C
/ \
R3 (C H2)m(CO)nO(C H2)0(AO)pR4
wherein R1 and R2 individually represent hydrogen atom or methyl group; R3
represents
hydrogen or -COOM group wherein M is a hydrogen atom or an alkali metal; (AO)p
represents linear repeating ethylene oxide groups and "p" represents the
average
number of repeating ethylene oxide groups and is an integer from 5 to 23; "m"
represents an integer of 0 to 2; "n" represents an integer of 0 or 1; "o"
represents an
integer of 0 to 4; and R4 represents a hydrogen atom or Ci to C4 alkyl group;
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(B) unsaturated carboxylic acid monomer represented by structural formula:
/R6
R7 C(0)OM
wherein R6 and R6 individually represent hydrogen atom or methyl group; R7
represents
hydrogen or -COOM group; M is a hydrogen atom or an alkali metal; and,
optionally,
(C) unsaturated, water-soluble hydrophilic monomer represented by structural
formula:
tN\, R1I0
"C=C
\X
R9
wherein R8, R9 and R1 each independently represent a hydrogen atom or methyl
group; X
represents C(0)NH2, C(0)NHR11, C(0)NR12R13, SO3H, C6H4S03H, or
C(0)NHC(CH3)2CH2S03H, or mixture thereof, wherein R11, R12, and R13 each
independently
.. represent a C1 to C5 alkyl group; and wherein the molar ratio of component
(A) to component
(B) is from 20:80 to 50:50, and further wherein the molar ratio of component
(C) to the sum of
component (A) and component (B) is 0:100 to 20:80; and wherein said at least
one
polycarboxylate comb type co-polymer is devoid of repeating oxyalkylene units
having three or
more carbon atoms or more, and is devoid of branched repeating oxyalkylene
units.
In preferred embodiments, the copolymer formed from components (A), (B), and
optionally (C) has a weight-average molecular weight of 14,000-25,000, and
more preferably
15,000-20,000, as measured by gel permeation chromatography (using
polyethylene glycol as
standards and with conditions described in further detail hereinafter). The
present invention
also relates to cementitious compositions, including concrete and mortar, made
according to
.. the exemplary method described above.
The present invention further provides a method for achieving low-to-mid-range
reduction
of hydration water in concrete or mortar mixes using at least one
polycarboxylate
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comb copolymer, comprising: combining with water and cement to form a
hydratable
cementitious mixture, wherein low-range and mid-range water reduction is
achieved at below
12 percent water cut and wherein the water/cement ratio is at least 0.45 and
no greater than
0.75, at least one air detraining agent and the at least one polycarboxylate
comb copolymer
having a weight average molecular weight of 14,000 ¨25,000, the at least one
polycarboxylate
comb copolymer being formed from the following monomer components:
(A) polyoxyalkylene monomer represented by structural formula:
R1
\ /R2
C ____________________________ C
/ \
R3 (C H2)m(C 0)nO(C H2)0(AO)pR4
wherein R1 and R2 individually represent hydrogen atom or methyl group; R3
represents
.. hydrogen or -COOM group wherein M is a hydrogen atom or an alkali metal;
(AO) p represents
linear repeating ethylene oxide groups and "p÷ represents the average number
of repeating
ethylene oxide groups and is an integer from 5 to 23; "m" represents an
integer of 0 to 2; "n"
represents an integer of 0 or 1; "o" represents an integer of 0 to 4; and R4
represents a
hydrogen atom or Ci to C4 alkyl group;
(B) unsaturated carboxylic acid monomer represented by structural formula:
R6 R6
\ /
/C ____________________________________ C
/ \
R7 C(0)0M
wherein R6 and R6 individually represent hydrogen atom or methyl group; R7
represents
hydrogen or -COOM group; M is a hydrogen atom or an alkali metal; and
(C) unsaturated, water-soluble hydrophilic monomer represented by
structural
formula:
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R8 Rio
\ /
/C ¨ C
/ \
R9 X
wherein R8, R9 and R1 each independently represent a hydrogen atom or methyl
group; X
represents C(0)NH2, C(0)NHR11, C(0)NR12R13, SO3H, C6H4S03H,
C(0)NHC(CH3)2CH2S03H,
or mixture thereof, wherein R11, R12, and R13 each independently represent a
Ci to C5 alkyl
group; and wherein the molar ratio of component (A) to component (B) is from
20:80 to 30:70,
and further wherein the molar ratio of component (C) to the sum of component
(A) and
component (B) is 0:100 to 10:90; and wherein the at least one polycarboxylate
comb copolymer
is devoid of oxyalkylene units having three or more carbon atoms, and is
devoid of branched
oxyalkylene units.
The present invention further provides a method for achieving low-to-mid-range
reduction
of hydration water in concrete or mortar mixes using at least one
polycarboxylate comb
copolymer, comprising: combining with water and Portland cement optionally
blended with fly
ash, granulated blast furnace slag, or limestone to form a hydratable
cementitious mixture,
wherein low-range to mid-range water reduction is achieved at below 12 percent
water cut and
no less than 3 percent water cut and wherein the water/cement ratio is at
least 0.51 and no
greater than 0.66, at least one air detraining agent and at least one
polycarboxylate comb
copolymer having a weight average molecular weight of 14,000 ¨ 22,000, the at
least one
polycarboxylate comb copolymer comprising the following monomer components (A)
and (B):
(A) polyoxyalkylene monomer represented by structural formula:
R1
\ /R2
C ____________________________ C
/ \
R3 (C H2)m(CO)nO(C H2)0(AO)pR4
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wherein R1 and R3 individually represent hydrogen; R2 represents hydrogen or
methyl group; (AO)p
represents linear repeating ethylene oxide groups and "p" represents the
average number of
repeating ethylene oxide groups and is an integer from 10 to 23; "m"
represents an integer of 0; "n"
represents an integer of 1; "o" represents an integer of 0; and R4 represents
a hydrogen atom or Ci
to C3 alkyl group; and
(B) an acrylic or methacrylic acid monomer;
and wherein the molar ratio of component (A) to component (B) is from 20:80 to
30:70; and
wherein the at least one polycarboxylate comb copolymer is devoid of
oxyalkylene units having three
or more carbon atoms, and is devoid of branched oxyalkylene units.
The present invention further provides a cementitious material made by the
method as
described herein.
Further benefits and features of the invention will be discussed in greater
detail hereinafter.
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Detailed Description of Exemplary Embodiments
As summarized previously, the present invention provides method and
cementitious compositions whereby low-to-mid range water reduction is achieved
using
specific structures and sizing within the polycarboxylate comb-type polymer
structure.
The term "cementitious" refers to materials that comprise Portland cement or
which otherwise function as a binder to hold together fine aggregates (e.g.,
sand),
coarse aggregates (e.g., crushed gravel), or mixtures thereof. he term
"cement" as
used herein includes hydratable cement and Portland cement which is produced
by
pulverizing clinker consisting of hydraulic calcium silicates and one or more
forms of
calcium sulfate (e.g., gypsum) as an interground additive. Typically, Portland
cement is
combined with one or more supplemental cementitious materials, such as
Portland
cement, fly ash, granulated blast furnace slag, limestone, natural pozzolans,
or
mixtures thereof, and provided as a blend.
The term "hydratable" as used herein refers to cement and/or cementitious
materials that are hardened by chemical interaction with water. Portland
cement clinker
is a partially fused mass primarily composed of hydratable calcium silicates.
The
calcium silicates are essentially a mixture of tricalcium silicate (3CaO=Si02
"C3S" in
cement chemists notation) and dicalcium silicate (2CaO=Si02, "C2S") in which
the
former is the dominant form, with lesser amounts of tricalcium aluminate
(3CaO.A1203,
"C3A") and tetracalcium aluminoferrite (4Ca0A1203=Fe203, "C4AF"). See e.q.,
Dodson,
Vance H., Concrete Admixtures (Van Nostrand Reinhold, New York NY 1990), page
1.
The term "concrete" as used herein refers generally to a hydratable
cementitious
mixture comprising water, cement, sand, a coarse aggregate such as crushed
gravel or
.. stone, and one or more optional chemical admixtures.
As used herein, the term "copolymer" or "polymer" refers to compounds
containing constituents derived or formed from the use of two different
monomer
components (designated as components "A" and "B") and optionally from the use
of
three different monomer components (i.e., further including at least one
optional
monomer designated as "C"), as described in exemplary methods of the invention
and
cementitious compositions made by the methods of the invention.
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Thus, an exemplary method of the present invention comprises: combining with
water and hydratable cement, to form a hydratable mixture having a
water/cement (w/c)
ratio of at least 0.40 and more preferably at least 0.45, and wherein the w/c
ratio is no
greater than 0.80 and more preferably no greater than 0.75, at least one air
detraining
agent and at least one polycarboxylate comb type polymer having the following
monomeric constituents:
(A) polyoxyalkylene monomer represented by structural formula:
R1
/R2
C ____________________________ c
R3 (c Hom(c 0)no(cH2)0(A0)pR4
wherein R1 and R2 individually represent hydrogen atom or methyl group; R3
represents hydrogen or -COOM group wherein M is a hydrogen atom or an alkali
metal;
(AO)p represents linear repeating ethylene oxide groups and "p" represents the
average
number of repeating ethylene oxide groups and is an integer from 5 to 23 (more
preferably, "p" is an integer from 5 to 15; and, most preferably, 8 to 12);
"m" represents
an integer of 0 to 2; "n" represents an integer of 0 or 1; "o" represents an
integer of 0 to
4; and R4 represents a hydrogen atom or C1 to C4 alkyl group (most preferably,
R4
represents a Ci or methyl group);
(B) unsaturated carboxylic acid monomer represented by structural formula:
/R6
/C ____________________________________ C
R7 C(0)0M
wherein R6 and R6 individually represent hydrogen atom or methyl group; R7
represents
hydrogen or -COOM group; M is a hydrogen atom or an alkali metal; and,
optionally,
(C) unsaturated, water-soluble hydrophilic monomer represented by structural
formula:
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R8 R10
/C = C
R9 X
wherein R8, R9 and R19 each independently represent a hydrogen atom or methyl
group; X represents C(0)NH2, C(0)NHR11, C(0)NR12R13, SO3H, C6H4S03H, or
C(0)NHC(CH3)2CH2S03H, or mixture thereof, wherein R11, R12, and R13 each
independently represent a Ci to C5 alkyl group; and wherein the molar ratio of
component (A) to component (B) is from 20:80 to 50:50, and further wherein the
molar
ratio of component (C) to the sum of component (A) and component (B) is 0:100
to
20:80; and wherein said at least one polycarboxylate comb type co-polymer is
devoid of
repeating oxyalkylene units having three or more carbon atoms or more, and is
devoid
of branched repeating oxyalkylene units.
In exemplary methods of the present invention, the hydratable cementitious
mixture is a concrete (which contains aggregates) designed for low-to-mid
range water
reduction applications, wherein the cement-to-concrete ratio is 240 to 340
kg/m3. This
contrasts with concretes typically used with superplasticizers designed for
high range
water reduction (HRWR) wherein the cement-to-concrete is usually at least 350
kg/m3.
In further exemplary embodiments, the molar ratio of component (A) to
component (B) is, preferably, from 20:80 to and including 50:50; more
preferably, from
25:75 to and including 35:65; and, most preferably, from 25:75 to and
including 30:70.
The molar ratio of component (C) to the sum of component (A) and component
(B) ranges from 0:100 to 20:80, and more preferably from 0:100 to 10:90. When
component (C) is present, the range is more preferably from 0.25:99.75 to
10:90.
The term "comprises" when used to describe the monomer components means
that the polycarboxylate copolymer is formed from monomer components (A), (B),
and
optionally (C) and may be formed from additional monomers (i.e., in addition
to) having
different structure or groups apart from what has been described for monomers
(A), (B),
and (C); whereas "consists essentially of" means, depending upon context, that
constituents of the polycarboxylate copolymer are formed from using monomer
components (A) and (B) only or from using monomer components (A), (B), and (C)
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only. Hence, in exemplary methods of the invention, the polycarboxylate
copolymer
may be formed using monomer components (A) and (6) only, or using (A), (6),
and (C)
only.
The weight-average molecular weight of the polycarboxylate copolymer is
14,000-25,000 as measured by gel permeation chromatography (GCP) using
polyethylene glycol (PEG) as standards and in accordance with the GPC
conditions
described in Example 1 below. More preferably, the weight-average molecular
weight
of the polycarboxylate copolymer polymer is 15,000-20,000 in accordance with
the
GPC conditions described in Example 1 below.
Examples of monomers for component (A) include, but are not limited to,
poly(ethylene glycol) methyl ether acrylate, poly(ethylene glycol) methyl
ether
methacrylate, poly(ethylene glycol) methyl ether maleate monoester,
poly(ethylene
glycol) methyl ether fumarate monoester, N-poly(ethylene glycol) acrylamide, N-
poly(ethylene glycol) methacrylamide, poly(ethylene glycol) vinyl ether,
poly(ethylene
glycol) allyl ether, poly(ethylene glycol) methallyl ether, poly(ethylene
glycol) isoprenyl
ether, poly(ethylene glycol) vinyloxybutylene ether, wherein the nominal
molecular
weight of the polyoxy ethylene-containing monomer of component A is in the
range of
300 to 1,600 and more preferably in the range of 500 to 1,200 (again using PEG
as
standards and GPC chromotagrphy conditions as described in Example 1 below).
Examples of monomer component (B) include, but not limited to, acrylic acid,
methacrylic acid, maleic acid, C1-C4 alkyl maleic monoester, maleic monoamide,
N-(C1-
C4) alkyl maleic monoamide, fumaric acid, C1-C4 alkyl fumaric monoester, N-(C1-
C4)
alkyl fumaric monoamide, crotonic acid, itaconic acid, or mixtures thereof.
Examples of unsaturated, water-soluble monomer of optional monomer
component (C) include, but not limited to, acrylamide, methacrylamide, N-alkyl
acrylamide, N-alkyl methacrylamide, N,N-dialkyl
acrylamide, N,N-dialkyl
methacrylamide, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic
acid, 3-
acrylamido-2-methylpropane sulfonic acid, styrene sulfonic acid, salts of
these acids, or
mixtures thereof.
A conventional air detraining (defoaming) agent may be used in combination
with
the polycarboxylate copolymer as contemplated within the present invention,
and used
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in an amount as deemed necessary or desired by the admixture formulator or
applicator.
As further example of air detraining agents which can be employed in the
present invention, EP 0 415 799 B1 of Gartner taught air-detraining nonionic
surfactants which included phosphates (e.g., bributylphosphate), phthalates
(e.g.,
diisodecylphthalate), and polyoxypropylene-polyoxyethylene block copolymers
(which
are not deemed to be superplasticizers) (See EP 0 415 799 B1 at page 6, II. 40-
53). As
another example, US 5,156,679 of Garner taught use of alkylate alkanolamine
salts
(e.g., N-alkylalkanolamine) and dibutylamino-w-butanol as defoamer. US
6,139,623 of
Darwin et at. disclosed antifoaming agents selected from phosphate esters
(e.g.,
dibutylphosphate, tributylphosphate), borate esters, silicone derivatives
(e.g., polyalkyl
siloxanes), and polyoxyalkylenes having defoaming properties. US 6,858,661 of
Zhang
et at. disclosed a tertiary amine defoamer having an average molecular weight
of 100-
1500 for creating stable admixture formulations. As yet another example, US
patent
8,187,376 of Kuo et al., disclosed the use of a polyalkoxylated polyalkylene
polyamine
defoamer.
As another example of an air detraining agents which can be employed in the
present invention, US 6,545,067 of Buchner et al. (BASF) disclosed butoxylated
polyalkylene polyamine for reducing air pore content of cement mixes. US
6,803,396 of
Gopolkrishnan et al. (BASF) disclosed low molecular weight block polyether
polymers
described as containing ethylene oxide and propylene oxide units as
detrainers. In
addition, US 6,569,924 of Shendy et al. (MBT Holding AG) disclosed the use of
solubilizing agents for solubilizing water-insoluble defoamers.
Further compositions and methods of the invention may further comprise or
include the use of at least one other agent selected from the group consisting
of (i) a
non-high range water reducer (non-HRWR) such as (sodium gluconate); (ii) an
alkanolamine (such as triethanolamine, triisopropanolamine,
diethylisopropanolamine,
or mixture thereof); (ii) a second defoamer which is different in terms of
chemical
structure from the first defoamer employed, (iv) an air-entraining agent such
as a higher
trialkanolamine such as triisopropanolamine or diethylisopropanolamine, a
lignosulfonate, a naphthalene sulfonate, a melamine sulfonate, an oxyalkylene-
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containing non-HRWR plasticizer, an oxyalkylene-containing shrinkage reducing
agent
(which does not function as a HRWR additive), or a mixture thereof.
While the invention is described herein using a limited number of embodiments,
these specific embodiments are not intended to limit the scope of the
invention as
otherwise described and claimed herein. Modification and variations from the
described
embodiments exist. More specifically, the following examples are given as a
specific
illustration of embodiments of the claimed invention. It should be understood
that the
invention is not limited to the specific details set forth in the examples.
All parts and
percentages in the examples, as well as in the remainder of the specification,
are based
on weight or percentage by weight unless otherwise specified.
Further, any range of numbers recited in the specification or claims, such as
that
representing a particular set of properties, units of measure, conditions,
physical states
or percentages, is intended to literally incorporate expressly herein by
reference or
otherwise, any number falling within such range, including any subset of
numbers within
.. any range so recited. For example, whenever a numerical range with a lower
limit, RL,
and an upper limit RU, is disclosed, any number R falling within the range is
specifically
disclosed. In particular, the following numbers R within the range are
specifically
disclosed: R = RL + k*(RU -RL), where k is a variable ranging from 1% to 100%
with a
1% increment, e.g., k is 1%, 2%, 3%, 4%, 5%. ... 50%, 51%, 52% ...95%, 96%,
97%,
.. 98%, 99%, or 100%. Moreover, any numerical range represented by any two
values of
R, as calculated above, is also specifically disclosed.
Example 1
This section describes an exemplary process for making polycarboxylate low-to-
mid-range plasticizer for use in the present invention. A three-neck round
bottom flask
is fitted with a mantle heater, and a thermocouple is connected to a
temperature
controller and mechanical stirrer. A reactor is charged with de-ionized water,
purged
with argon gas, and then heated to 65 C. A solution of poly(ethylene
glycol)methyl
ether methacrylate (MPEGMA), methacrylic acid (MAA) or acrylic acid (AA), 3-
mercaptopropionic acid and de-ionized water is prepared in advance.
Separately, a
solution of ammonium persulfate in de-ionized water is prepared. Once the
temperature
of the reactor reaches 65 C, both solutions are added drop-wise over a period
of 1.5
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hour while stirring. After the addition is completed, the reaction is
continued for another
2.0 hours at 68-70 C and then stopped by cooling to ambient temperature.
GPC Conditions. The weight-average molecular weights of the resulting
polymers (and other oxyalkylene containing molecules) can be measured by
employing
gel permeation chromatography (GPC) using the following separation columns and
polyethylene glycol (PEG) as standards:
ULTRAHYDROGELTm 1000,
ULTRAHYDROGELTm 250 and ULTRAHYDROGELTm 120 columns. The GPC
processing conditions are as follows: 1% aqueous potassium nitrate as elution
solvent,
flow rate of 0.6 mL/min., injection volume of 80 pL, column temperature at 35
C, and
refractive index detection.
Various properties of the polycarboxylate (co)polymer sample as well as of
reference samples are listed below in Table 1.
Table 1
Molar ratio Weight-
Sample MW of MPEGMA MAA AA ofMPEGMA to average
Identification MP EGMA [mol] [mol] [mol]
MAA or AA Mw [Da]
Sample 1 500 0.50 1.50 - 1.0 : 3.0 16k
Sample 2 500 0.50 - 1.40 1.0 : 2.8 20k
Reference 1 2,000 0.50 1.50 - 1.0 : 3.0 .. 17k
Reference 2 5,000 0.50 1.50 - 1.0 : 3.0 20k
Reference 3') 2,000 1.0 : 4.4 17k
1) Reference 3 is a commercial
polycarboxylate product.
Example 2
This example illustrates the water-reducing effect of polycarboxylate polymers
of
the present invention by measuring the slump of concrete. Concrete mixes are
made
fabricated using the following proportions: cement (300 kg/m3), sand (772
kg/m3),
stone (1,158 kg/m3), and water. The amount of water is varied depending on the
type
of cement and the weight ratios of water to cement (w/c) are 0.51, 0.58 and
0.55 for fly
ash-blended cement CEM II/B-V 32.5R, slag-blended cement CEM II/B-S 32.5R, and
limestone-blended cement CEM II/A-LL 42.5R, respectively.
The results are shown in Table 2 wherein the slump was measured as a function
of percentage of active polymer dosage to cement.
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Table 2
CEM II/B-V 32.5R CEM II/B-S 32.5R CEM II/A-LL
42.5R
Sample wic= 0.51 wic= 0.58 wic= 0.55
Identification Dosage Slump Dosage Slump Dosage Slump
[%sic] [mm] [%sicl [mm] [%sic] [mm]
0 75 0 60 0 70
Sample 1 0.04 115 0.05 140 0.065 120
0.06 150 0.07 200 0.08 170
0 75 0 60 0 70
Reference 1 0.06 100 0.05 115 0.065 110
0.09 140 0.07 180 0.08 135
0 75 0 60 0 70
Reference 2 0.06 85 0.05 85 0.065 100
0.09 100 0.07 155 0.08 120
As shown in Table 2, Sample 1 exhibited higher slump than both Reference
samples at equal polymer dosages. These results indicate the greater water-
reducing
efficiency of the polycarboxylate polymers having lower molecular weight
poly(ethylene
glycol) units, at these w/c ratios.
Exam!)le 3
The performance of the polycarboxylate polymer (Sample 2) made according to
Example 1 was evaluated in concrete with a commercially available polymer
(Reference 3). The test protocol described in Example 2 was employed, except
that the
weight ratios of water to cement were 0.53, 0.57, and 0.55 for fly ash-blended
cement
CEM II/B-V 32.5R, slag-blended cement CEM II/B-S 32.5R, and limestone-blended
cement CEM II/A-LL 42.5R, respectively. The results are summarized in Table 3.
Table 3
CEM II/B-V 32.5R CEM II/B-S 32.5R CEM II/A-LL 42.5R
Sample w/c= 0.53 wIc= 0.57 , w/c= 0.55
Identification Dosage Slump Dosage Slump Dosage Slump
Pk sic] [mm] [% sic] [mm] [% sic] [mm]
0 75 0 60 0 80
Sample 2 0.05 130 0.04 115 0.07 155
0.08 170 0.06 185 0.10 180
0 75 o 60 0 80
0.05 120 0.04 105 0.07 130
Reference 3
0.08 145 0.06 150 0.10 150
0.10 170 - -
The results in Table 3 indicate that at the water/cement ratio indicate that
the
polycarboxylate polymers made in accordance with the present invention
outperformed
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the commercially available polycarboxylate polymer having higher molecular
weight
poly(ethylene glycol) groups.
Example 4
This example compares the slump retaining performance of the polycarboxylate
polymer (Sample 2) against a commercially available polymer (Reference 3). The
test
protocol described in Example 2 was employed, except that slump was measured
at
10-minutes and 30-minutes after hydration. Dosage of polymer Sample 2 was
adjusted
such that it was 37% lower than that of polymer sample Reference 3 to obtain
comparable initial slumps at the 10-minute mark.
Table 4
CEM II/A-LL 42.5R
w/c= 0.55
Sample ID
Dosage Slump [mm]
[Vo sic] 10 min 30 min
Sample 2 0.05 135 85
Reference 3 0,08 140 85
It is evident from Table 4 that both materials exhibit similar slump retaining
behavior although the dosage of the polycarboxylate polymer made in accordance
with
the teachings of the present invention was much lower.
Example 5
This example evaluates the slump retaining performance of a mixture of sodium
gluconate (SG) and Sample 2 polycarboxylate polymer, as well as a mixture of
SG with
the commercially available polymer of Reference 3. For both mixtures, the
amounts as
well as the weight ratio of SG to polymer were identical. Concrete mixes were
fabricated using the following proportions: cement (340 kg/m3), sand (921
kg/m3),
stone (788 kg/m3), and water (224 kg/m3). The slump was measured at 10, 30,
and 60
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minute intervals. Table 5 shows the results obtained with Portland cement CEM
I 42.5R
at water to cement weight ratio of 0.66.
Table 5
CEM I 42.5
Sample w/c=0.66
Identification Dosage Slump [mm]
1% s/c] 10 min 30 min 60 min
SG & Sample 1 0.26 165 120 110
SG & Reference 3 0.26 125 95 85
The results in Table 5 clearly indicate that the water-reducing mixture
containing
the polycarboxylate copolymer of Sample 1 of the present invention exhibits
much
better slump retaining performance than the mixture containing commercial
polymer
Reference 3.
Example 6
In this example, the water-reducing performance is evaluated in concrete mixes
wherein the weight ratios of water to cement were much lower as a high-range
water
reducer. The concrete mixes were prepared in the traditional manner as
follows:
cement (370 kg/m3), sand (700 kg/m3), stone (1,191 kg/m3), and water. The
amount of
water varied depending on the type of cement and the weight ratios of water to
cement
were 0.41, 0.41, and 0.40 for fly ash-blended cement CEM II/B-V 32.5R, slag-
blended
cement CEM II/B-S 32.5R, and ordinary Portland cement, respectively. The
slumps
were measured at various dosages and are summarized in Table 6.
Table 6
CEM II/B-S 32.5R CEM II/B-V 32.5R Normal Portland
Cement
Sample
Identification w/c=0.41 w/c=0.41 w/c=0.40
Dosage Slump Dosage Slump Dosage Slump
1% s/c] [mm] [% s/c] [mm] [% s/c] [mm]
0 30 0 40 0 30
Sample 1 0.07 100 0.07 140 0.13 70
0.09 150 0.19 200
0 30 0 40 0 30
Reference 1 0.07 120 0.07 170 0.10 95
0.09 215 0.13 195
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The results shown in Table 6 indicate that the slump values achieved by using
polycarboxylate copolymer Sample 1 of the present invention were significantly
lower
than those obtained by using Reference 1 at the low water-to-cement ratios,
confirming
that superplasticizers which are typified by Reference 1 have far inferior
performance
compared to the copolymers used in accordance with the teachings of the
present
invention.
The results also confirm that the copolymer having lower molecular weight
poly(ethylene glycol) groups performed more suitably at low-to-mid water
ranges
compared to copolymers having higher molecular weight poly(ethylene glycol)
groups.
This behavior at low water to cement ratios is surprisingly opposite to that
when the
water to cement ratios are higher.
The principles, preferred embodiments, and modes of operation of the present
invention have been described in the foregoing specification. The invention
which is
intended to be protected herein, however, is not to be construed as limited to
the
particular forms disclosed, since these are to be regarded as illustrative
rather than
restrictive. Skilled artisans can make variations and changes based on the
specification without departing from the spirit of the invention.
